Hydraulic pump



R. C. HARE HYDRAULIC PUMP May 26, 1970 4 Sheets-Sheet l Original Filed April 26, 1966 ATTORNEY) May 26, 19,70 R. c. HARE 3,514,223

HYDRAULIC PUMP Original Filed April 26, 1966 4 Sheets-Sheet 0 jrg h3..

I8 24 33 74d 76 94 I2 i, 652 84 f es 56 I4 se 4e INVENTOR RICHARD C. HARE BY @MM ATTORNEY,

May 26, 1970 R. c. HARE 3,514,223

' HYDRAULIC PUMP Original Filed April 26, 1966 4 Sheets-Sheet 5 INVENT OR @Ma/QM ATTORNEY 5 4,Sheets-Sheet 4.

m m w m ATTORNEYS May 26, 1970 R. c. HARE HYDRAULIC PUMP Original Filed April 26. 1966 United States Patent O 3,514,223 HYDRAULIC PUMP Richard C. Hare, Wauwatosa, Wis., assigner to Applied Power Industries, Inc., Milwaukee, Wis., a corporation of Wisconsin Continuation of application Ser. No. 545,321, Apr. 26, 1966. This application Aug. 19, 1968, Ser. No. 757,519 Int. Cl. F04b 9/00, 1/14, 7/00 U.S. Cl. 417-269 4 Claims ABSTRACT OF THE DISCLOSURE A hydraulic pump of the type having a plurality of parallel cylinders with pistons therein driven by a rotating wobble plate. The pump includes a removable and plate assembly having a plurality of outlet bores communicating with the cylinders and further having check valve units wholly disposed within the end plate between the cylinders and the outlet bores, whereby said end plate is removeable as a unit.

This application is a streamlined continuation of 545,- 321 led Apr. 26, 1966, now abandoned.

This invention relate generally to pumps and more particularly to hydraulic pumps of the type that incorporates a plurality of reciprocating pistons driven by a rotating wobble plate.

Prior art pumps of the type to which this invention generally relates are, on the whole, rather expensive in that they require parts which are machined to high degrees of tolerance and require rather complicated means for reducing the friction between stationary and relatively rotating parts thereof. For example, the reciprocating pistons require at least two spring-biased check valves associated with each piston unit. In each of these check valves the prior art pumps require seats machined to a high degree of accuracy to maintain leakage between the valving member and the seat to a minimum.

Prior art pumps of the type referred to also require friction reducing means between their rotating wobble plate and the portion of the rotationally stationary pistons which engage the surface of the wobble plate. One such means comprises a roller bearing structure positioned between the portion of the piston against which the wobble plate drives and the wobble plate driving surface. Another means for reducing this friction consists of hydraulic channeling to provide a hydraulic lrn or hydrostatic balance between the relatively moving surfaces.

Prior art pumps have furthermore been limited to a designed in hydraulic fluid output configuration thereby limiting the adaptability of the pump to a single design use.

It is an object of this invention to provide a novel hydraulic pump which is less expensive than heretofore available by providing means to minimize the need for high tolerance machined ball check valve seats in the pump structure.

It is another object of this invention to furnish a novel hydraulic pump which requires fewer parts than heretofore necessary by providing means to overcome friction between the portions of the reciprocating pistons engaging the wobble plate without resorting to anti-friction roller bearings or hydrostatic balance techniques.

It is still another object of this invention to furnish a new hydraulic pump in which the hydraulic output configuration can be readily altered according to the use requirements of the pump.

These and other objets of the invention will become more apparent to those skilled in the art by reference to the following detailed description when viewed in light 3,514,223 Patented May 26, 1970 ICC of the accompanying drawings, wherein like elements throughout the figures thereof are indicated by like numerals and wherein:

FIG 1 is a sectional view, in elevation, of a pump embodying features in accordance with this invention;

FIG. 2 is an end View, partly in section, of the pump of FIG. 1 showing the detail of an end plate controlling the hydraulic output configuration of the pump;

FIG. 3 is a sectional view of a portion of the pump of FIG. l illustrating, in detail, a reciprocating piston and the resultant hydraulic flow;

FIG. 3a is an enlarged and broken away sectional view of a portion of the detail illustrated in FIG. 3;

FIG. 4 is a view similar to that of FIG. 2 showing another end plate controlling the hydraulic output contiguration of the pump in accordance with the invention;

FIG. 5 is a view of the obverse side of the end plate of FIG. 4;

FIG. 6 is a sectional view of the end plate of FIG. 4, taken along the lines 6 6 thereof, installed on a pump in accordance with the invention; and

FIG. 7 is a sectional view of the end plate of FIG. 4 similar to the view in FIG. 6 taken along the lines 7-7 of FIG. 4.

Turning now to FIG. l of the drawings, a pump comprising a housing, shown generally at 10, a barrel section 33 and an end plate shown generally at 12 is provided with a wobble plate 14 having a slanted or non radially extending llat transverse cam surface 15. The plate 14 is rotatably mounted in the housing on a tapered roller bearing assembly 16 and a rotatable shaft 18 fixed to the wobble plate by means of a key 20 disposed in a keyway 22. The inner end of the shaft 18 is rotatably mounted in the housing by means of a needle bearing assembly 24 and is axially xed with respect to the wobble plate 14 by means of a radially extending ring 26 which engages the transverse surface of a recess 28 coaxially disposed in the surface 15 of the wobble plate. An annular elastomeric seal 3i) engages the peripheral surface of the shaft 18 proximate the point where the shaft traverses the housing 10. A second key 32 is disposed in the outer end of the shaft 18 to serve as a point of attachment for a driving means (not shown).

A barrel section 33 defining a plurality of axially disposed cylindrical bores 34 is mounted to the end plate end of the housing 10 by a plurality of bolts 35. A piston 36 is disposed in each of the bores 34 for reciprocation therein. Each of the pistons 36 is provided with a wobble-plateengaging shoe 38 swivelly connected thereto through a ball joint 40. The shoes 38 are formed of bronze (Mueller 602) while the wobble plate 14 is composed of a castiron alloy (spec H 511.850). The combination of the piston shoe design and the materials used permits a high velocity under high loadings with a minimum of friction thereby obviating a requirement for anti-friction bearings or hydrostatic balance between the contacting surfaces. An annular collar 42, fixed to each of the pistons 36 proximate the ball joint 40, engages a compression spring 44 coaxially disposed around the piston. The compression spring 44 is disposed between the collar 42 into an annular recess coaxially disposed around the cylindrical bores 34 to bias the pistons 36 and the shoes 38 toward the surface 15 of the wobble plate.

Each of the pistons 36 is provided with an internal coaxially disposed bore 46 which extends from an inlet 48 in the peripheral surface thereof proximate the collar 42 to the free end of the piston proximate the end plate I12. The bore 46 is provided with an enlarged portion 50, the intersection therebetween being defined by a tapered, generally transversely extending seat 52. A ball valving member 54- is disposed in the enlarged portion 50 and is ybiased against the seat 52 by a check valve compression spring 56. An annular collar 58 is threaded into the open end of the enlarged portion 50 and, on its inner transverse surface, abuts an annular spacer 60 which, in turn, supports a ball stop member 62 threaded in the open end thereof. The ball stop member 62 comprises an axially extending cylinder portion 64, which engages the ball valving member 54, to limit axial movement thereof, and a transversely extending flange 66 which is provided with a plurality of axially extending bores 68 to provide passage of the fluid being pumped thereby. The aforedescribed piston structure is similar to those known in the art and it should be understood that suitable structures other than that specifically described can be utilized in this portion of the pump.

The housing is formed to define an inlet chamber 70 which encompasses the wobble plate 14 and a portion of the shaft 18. A threaded inlet fitting 72 is provided through the housing to furnish communication between the inlet chamber 70 and a source of hydraulic fluid (not shown).

The end plate 12 is formed, to encompass an outlet manifold system consisting of end plate inlet bores 74a through 74f (FIG. 2) extending axially into said end plate and disposed in registration with each of the cylindrical bores 34 and communicating with a main outlet bore 76 disposed transversely to the axis of the end plate. This latter-described bore communicates with a threaded outlet fitting 78 which fitting furnishes means for connecting the pump to a pressure sink (not shown) to which the pressurized hydraulic output of the pump is directed.

An annular bushing insert 80 is disposed in each of the end plate inlet bores 74a through 74f, sealing being effected therebetween by an O ring 83 disposed in a cylindrical recess coaxially formed around each of the bores. A tapered annular seat 82 is coaxially disposed on the inner transverse face of the bushing 80 and is engaged by a ball valving member 84 which is biased thereagainst by a compression spring 86.

Referring specifically to FIG. 3a, the ball valving member 84 is formed of a hardened steel as is usual in the art. By configuring the seat 82 so that the angle is approximately 36 and by providing a bore-to-ball diameter ratio of 5 to 6, it is possible to provide a self seating capability for the valve by forming the seat of a soft steel. With this configuration and these materials, the ball 84 will deform the seat 82 during the initial operation of the pump to form a suitable seal therebetween. The abovedescribed seat angle and diameter ratio will result in an angle ,8 between a radius drawn to the point of tangency and the seat of approximately 92.5 prior to deformation of the seat by initial operation of the pump. This feature of the invention permits the use of check valve seats machined to lower tolerances than heretofore necessary thereby resulting in savings of cost and fabrication time for the pump.

A cylindrical ball stop pin 88 is mounted in a recess 90 behind the ball 84 and serves to provide means to limit the axial movement of the ball 84 as well as a guide for the spring 86.

Turning now to FIG. 2 of the drawings, an end view of the pump of FIG. 1 showing the transverse details of the end plate 12 is illustrated. Bolts 91 suitably disposed around the periphery of the end plate 12, attach the end plate to the barrel section 33. As is better seen in this figure, the end plate inlet bores 74a through 74f are symmetrically disposed in the inlet with the bores 74a and 74d directly communicative with the outlet tting 78 through the main transverse bore 76. Inlet bores '74b and 74jc are interconnected by a first lateral bore 92 which intersects the main bore 76 to provide communication with the outlet fitting 78. The inlet bores 74e and 74e are similarly connected by a second lateral bore 94 which also intersects the main bore 76 to provide intercommunication between the outlet fitting 78 and the latter-mentioned bores.

In operation, the pump, suitably hooked to a source of hydraulic fiuid through the inlet fitting 72r and a sink for pressurized fluid through the outlet fitting 78 by means of hydraulic conduits, is energized by rotation of the shaft 18. Rotation of the shaft 18 causes rotation of the wobble plate 14 which, because of the configuration of the slanted cam surface 15, causes alternate reciprocation of each of the pistons 36. Referring to FIG. l, the uppermost piston is illustrated substantially at its maximum point of intake stroke while the lowermost piston is at the opposite extreme substantially at its maximum displacement in the compression stroke. The remaining pistons are at intermediate stages between these extremes. In the compression stroke, the piston is driven by the slanted surface 15 of the wobble plate 14 and the shoe 38 while, during the intake stroke, the piston is displaced in the opposite direction in contact with the wobble plate 14 by bias of the spring 44. Because of the composition of the shoe and wobble plate as set forth above, there is no requirement for friction reducing means between the members and pump operates efficiently with the members in direct contact.

Referring specifically now to FIG. 3 of the drawings, one of the pistons 36 is shown during the compression stroke thereof. During the intake stroke, the cylinder 34 and the bore portions 46 and 50 have been filled with hydraulic fluid from the inlet chamber 70 through the bore inlet 48. As the direction of reciprocation of the piston changes and the piston travels towards the end plate end of the pump, the lball valving member 54 is moved against the tapered seat 52 under the influence of the compression spring 56 and the hydraulic fluid trapped downstream of the ball 54 thereby sealing hydraulic fluid in the cylinder 34. As the volume of the cylinder is decreased by movement of the piston 36, pressure is built up in the cylinder and the iball valving member 84 in the end plate 12 is displaced fro-m the tapered seat 82 thereby opening communication between the cylinder 34 and the main transverse bore 76 for expulsion of hydraulic fluid runder pressure through the outlet fitting 78 (FIG. 1). The compression stroke is identical for each of the pistons and, in the case of the pistons com-municating with the inlet bores 74b and 74f and inlet bores 74a` and 74e (FIG. 2), fluid is exhausted therefrom by way of the first and second lateral bores 92 (FIG. 2) and 94 respectively through the main transverse bore 76 and ultimately through the outlet fitting 78. In the embodiment of FIGS. 1 through 3 then, the output from each of the cylinders 34 is manifolded and exhausted at a single point, the outlet fitting 78.

In the inlet stroke, the above-described components function essentially in a reverse sequence with the piston changing direction and moving toward the wobble plate 14 from the position of the lowermost piston in FIG. l under the influence of the compression spring 44. Under these conditions, the pressure drops in the cylinder 34 and the end plate ball valving member 84 returns into sealing engagement with the seat 82 under the influence of the bias of the compression spring 86. As the piston moves away from the end plate end of the pump, the pressure in the cylinder 34 drops causing the ball valving member 54 to unseat dfue to the pressure differential thereacross. Hydraulic fluid then flows from the inlet chamber 70 through the bore inlet 48 into the cylinder through the bore portions 46 and 50 to again fill the cylinder.

In FIGS. 4 through 7, a variation in the pump in accordance with the invention is illustrated. In these figures, portions thereof corresponding to like portions in the pump shown in FIGS. 1 through 3 are indicated by like numerals only of the next highest order. The primary distinction between the pump of the embodiment of FIGS. 4 through 7 over the raforedescribed embodiment lies in the manifolding of the end plate 112. By fabricating a pump in accordance with the teachings of this invention, the manifolding and valving of the end plate is completely self-contained and utilized so that,

by substitution of end plates, the outlet manifolding configuration thereof may be practically and readily changed Without requiring modification to the pump body or mechanism itself. Furthermore, the components making up the end plate valving mechanism of both of the illustrated embodiments are identical so that the end plate may be manifolded as desired by simply altering the coring pattern thereof, the other components making Iup the valving elements in the end plates being interchangeable.

As will be seen by reference to the figures, the end plate is provided with a plurality of end plate inlet bores 174a through 174f disposed in a manner similar to those in the end plate of FIG. 1.

A main transverse bore 176 connects end plate inlet bores 174m and 174d to an outlet fitting 1785il A first diagonal bore 192, spaced axially from the lmain transverse bore 176, connects inlet bores 174b and 174e to a second outlet fitting 178b while a second diagonal bore 194, axially disposed between the main transverse bore 176 and the aforementioned diagonal bore, connects inlet bores 174e` and 174]l to a third outlet fitting 178C. Due to the axial offset of the first and second diagonal bores 192 and 194, it is necessary to provide axial passageways therefrom to communicate with the inlet bores 174b, 174C, 174e and 1741. This is accomplished 'by providing axially extending transfer bores 196b, 196e, 196e and 196]c to communicate with bores 174b, 174e, 174e and 174f respectively. This manifold arrangement affords connection of the end plate inlet bores, in pairs, to separate outlet fittings thereby providing for a split or division of the output of the hydraulic fluid. Obviously, other variations may be readily made in the manifolding of the end plate to 'meet other contingencies if required. For example, inlet bores 174a through 174:! could be manifolded into a common outlet while inlet bores 174e and 174)l could be connected to a second common outlet thereby providing split flow output of different volumes. Any variation or combination of multiple flow outlets, up to and including a separate outlet for each of the pistons, can obviously be provided by proper design of the end plate manifolding systems. The pump itself could also have any desired number of pistons as the use to which it is to be put or the design requirements dictate.

What has been set forth above is intended primarily as exemplary to enable those skilled in the art in the practice of the invention and it should, therefore, be understood that, within the scope of the appended claims, the invention may be practiced in other ways than as specifically described.

What is new and, therefore, desired to be protected by Letters Patent of the United States is:

1. A hydraulic pump comprising a housing defining an inlet chamber therein, means connecting said chamber to a source of hydraulic fluid, a shaft rotatably disposed through said chamber and extending through one end of said housing, a wobble plate having a slanted transverse cam surface thereto mounted on said shaft for rotation thereby at least the cam surface of said wobble plate being formed of cast iron alloy, a barrel section connected to said housing, said 'barrel section defining a plurality of axially aligned cylinders communicative at one end thereof with said chamber, a piston slidably disposed in each of said cylinders, each of said pistons having an axial bore therethrough communicating with said chamber, check valve means in each of said pistons to block flow of fluid therethrough in the direction of said chamber, a bronze shoe swivelly mounted on the chamber end of each. of said pistons to enga-ge the cam surface of said wobble plate, means to bias each of said pistons towards said wobble plate to maintain continuous contact between the cam surface and said shoe, an end plate removably connected to the free end of said barrel section, said end plate defining a plurality of outlet bores therein, at least one outlet fitting on said end plate, each of the outlet bores disposed to provide communication between one of said cylinders and an outlet fitting, and ball check valve means disposed in each of said outlet bores to block the flow therethrough in the direction of said cylinders, said check valve means including an annular soft steel bushing having a seat tapered approximately 36 to the center line coaxially formed in one end thereof, and a hard steel ball resiliently biased against said seat, the ratio of the diameter of the bore in said bushing to said ball being approximately 5 to 6 whereby initial operation of the check valve deforms said seat to conform to the contacted portion of said ball to thereby provide suitable sealing therebetween.

2. A pump in accordance with claim 1 wherein said end plate is provided with a single outlet fitting.

3. A pump in accordance with claim 1 wherein said end plate is provided with three outlet fittings axially and circumferentially spaced from one another and communicating with said outlet bores, inlet bores extending substantially transversely of said outlet bores into said end plate, and wherein said housing defines six symmetrically disposed cylinders in communication with said inlet bores, each of said inlet bores communicating with the outlet bores corresponding to a different pair of cylinders in said housing thereby manifolding each pair of cylinders to a different outlet fitting.

4. In a pump for hydraulic fiuid of the type in which pistons operating in parallel cylinders within a -barrel section connected to a pump housing are operated in their pumping stroke by a drive shaft carrying a non-radially extending fiat cam plate portion positioned opposite the ends of the cylinders, the improvement which comprises:

a shoe swivelly mounted on each of said pistons to engage said flat plate portion;

a single end plate having a plurality of outlet bores therein and a plurality of outlet fittings each communicating with at least one of said outlet bores, means connecting said end plate to said barrel section, at least one of said outlet bores being disposed to communicate with at least two of said cylinders, a check valve Wholly within said end plate in each of said outlet conduits to block flow therethrough in the direction of said cylinders, said check valves comprising an annular soft steel bushing having a seat tapered approximately 36 to the center line coaxially formed in one end thereof, and a hard steel ball resiliently biased against said seat, the ratio of the diameter of the bore in said bushing to said ball being approximately 5 to 6 whereby initial operation of the check valve deforms said seat to conform to the contacted portion of said ball to thereby provide suitable sealing therebetween, said end plate being removable to enable substitution of an end plate having a different arrangement of outlet fittings and bores communicating with different combinations of cylinders.

References Cited UNITED STATES PATENTS 1,757,139 5/1930 Platenberg. 2,455,289 11/1948 Baierlein 103-73 2,940,323 6/1960 Cousins et al 74-60 3,148,707 9/1964 SmyklO. 2,941,475 6/1960 Blair. 3,178,888 4/1965 Hampton 103-9 3,236,189 2/1966 Pasker.

WILLIAM L. FREEH, Primary Examiner US. Cl. X.R. 

